The present invention relates to rotary blowers of the Roots-type, and more particularly, to such blowers of the backflow-type.
As is well known, Roots-type blowers include lobed rotors meshingly disposed in transversely overlapping cylindrical chambers defined by a housing. Spaces between adjacent unmeshed lobes of the rotors transfer volumes of air from an inlet port opening to an outlet port opening, without mechanical compression of the air within the spaces. Stated another way, a Roots-type blower achieves pressure boost, not by internally compressing the air being transferred, but instead, achieves pressure boost simply by transferring a volume of air which is greater than the volume displacement of the device with which the blower is associated.
Typically, Roots-type blowers such as those described above are used as superchargers for vehicle engines, wherein the engine provides the mechanical input drive torque to the blower rotors. The volume of air transferred to the outlet port of the blower is then utilized to provide a pressure xe2x80x9cboostxe2x80x9d within the intake manifold of the vehicle engine, in a manner which is now well know to those skilled in the art, but which is only indirectly relevant to the present invention.
A typical Roots blower supercharger of the type sold commercially by the assignee of the present invention is illustrated and described in U.S. Pat. Nos. 5,527,168 and 5,893,355, both of which are assigned to the assignee of the present invention and incorporated herein by reference. In the typical Roots blower supercharger installation, the blower rotors rotate about axes which are oriented longitudinally (xe2x80x9cnorth-southxe2x80x9d) within the vehicle engine compartment. The mechanical input drive torque from the engine is transmitted to the blower by means of an input pulley and an input shaft disposed on the forward end of the blower. The input torque is transmitted to the pulley, and then by means of the input shaft to a pair of timing gears which are typically mounted on the forward ends of the rotor shafts and are included to insure that the rotors mesh, but do not make physical contact with each other, a requirement which is well know to those skilled in the art.
In the typical prior art Roots blower supercharger, in its conventional installation, the inlet port and the xe2x80x9cleading endxe2x80x9d of the rotors are disposed at the rearward end of the blower housing (so inlet air flows axially into the rotor chamber), and the xe2x80x9ctrailing endxe2x80x9d of the rotors and the larger (wider) portion of the outlet port are disposed toward the forward end of the blower housing, and typically, on the underside. Although the above-described conventional arrangement has been in widespread commercial use, and may be acceptable in some vehicle applications, it is not fully desirable in most vehicle applications, because of the need to provide ducting to communicate induction air from the forward portion of the engine compartment around a bend (with the ducting now extending forwardly), to the inlet port at the rearward end of the supercharger. In most of those applications, there is very little room, axially, between the rearward end of the supercharger and the cowl and dash sheet metal. If it is even possible to fit the inlet ducting into the space available, the resulting sharp bend (or turn) in the ducting reduces the air flow of the blower, and therefore, the overall performance of the blower.
The above-described arrangement also adds substantially to the total amount of ducting required, thus making it much more difficult and expensive to package the supercharger within the engine compartment. In an effort to improve the packaging of the blower and reduce the amount of ducting required, those skilled in the art have developed what is referred to as a xe2x80x9ctop inletxe2x80x9d blower, in which the duct carrying inlet air passes over the top of the blower, then turns downwardly to an inlet port on the upper side of the blower, typically, near the rearward end of the blower. Although such top inlet blowers require less ducting, there is still a sharp bend of the ducting down to the inlet port, and a requirement that the air flow make a sharp turn, thus providing less air flow through the blower than in the case of the rear inlet type. As is well known to those skilled in the blower art, having inlet air flow axially into the rotor chambers is inherently more efficient than having inlet air enter the rotor chamber from the top. In addition, the presence of the inlet ducting above the blower causes the overall assembly height to be excessive for most vehicle applications.
Accordingly, it is an object of the present invention to provide an improved rotary blower assembly, especially of the Roots blower type, useable as a vehicle supercharger, which overcomes the disadvantages of the prior art blower installations described above.
It is a more specific object of the present invention to provide such an improved blower assembly which makes it possible to substantially reduce the amount of inlet ducting required, as well as the occurrence of sharp bends in the ducting.
It is another object of the present invention to provide such an improved blower assembly and installation which accomplishes the above-stated objects, while at the same time making it possible to reduce the overall mounting height of the blower installation, including the inlet ducting.
The above and other objects of the invention are accomplished by the provision of an improved rotary blower of the backflow type comprising a housing, first and second meshed lobed rotors, each lobe having a leading end and a trailing end. The rotors are rotatably disposed in the housing for transferring relatively low pressure inlet port air to relatively high pressure outlet port air. First and second meshed timing gears are fixed to be non-rotatable relative to the first and second rotors, respectively, for preventing contact of the meshed lobes of the rotors. An input drive member is adapted to transmit an input drive torque to the first rotor, the housing defining an inlet port and an outlet port.
The improved rotary blower is characterized by the housing having a rearward end and a forward end, adapted to be oriented toward the forward end of a vehicle engine compartment, the input drive member extending forwardly from the forward end of the housing. The inlet port is disposed at the forward end of the housing adjacent the leading end of the rotors and being defined substantially by a forward end wall of the housing and being disposed above the input drive member. The housing includes a duct portion in open fluid communication with the inlet port, the duct portion extending forwardly and defining a forward duct opening.
In accordance with another aspect of the invention, the improved rotary blower is characterized by the duct portion extending both forwardly and transversely, whereby the forward duct opening is disposed transversely from the input drive member.